200 



ZOOLOGY. 



part of tlie thorax, and liciice when the outstretched wings 

 act upon the aii- as a fnlci'um all the weight of tlie body is 

 ])laced below this surface of suspension (Marey). The 

 flight of birds has been studied by Marey, who states that 

 "from the manner iu which the feathers of its wing lie 

 npon each other, it is evident that the resistance of the air 



Fig. 242.— Skeleton and outline of the Dove, c, cervical vertebra?: d, dorsal 

 vertebra?; /, lumbar vertebrte; (j\ coccyx; h. breast-bone, sternum; I, ribs; 

 k, slioulder l)laile, scapula; I, coracoid; V , Avish-boue, clavicles; m, humerus; 

 n, ulna; n', radius; p, car-pus; r, metaca,ipals and three digits; s, ischiatic 

 bone; w, pelvis; t^ ilium; v, femur; ;r, tibia; a', metatarsus; 6, digits. After 

 Liitken. 



can only act from below upwards, for iu the opjiosite direc- 

 tion tlie air would force for itself an easy passage by bend- 

 ing the long barbs of the feathers, wliich would no longer 

 sustain each other." The wing acts on the air like a wedge 

 or an inclined jihine, " in order to jirodnce a reaction against 

 this resistance which impels the body of the bird upward 

 and forward." 



